Earth's First Arctic Ozone Hole Recorded

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The high atmosphere over the Arctic lost an unprecedented amount
of its protective ozone earlier this year, so much that
conditions echoed the infamous ozone hole that forms annually
over the opposite side of the planet, the Antarctic, scientists
say.

"For the first time, sufficient loss occurred to reasonably be
described as an Arctic ozone hole," write researchers in an
article released Oct. 2 by the journal Nature.

The reactions that convert less reactive chemicals into
ozone-destroying ones take place within what is known as the
polar vortex, an atmospheric circulation pattern created by the
rotation of the Earth and cold temperatures. This past winter and
spring saw an unusually strong polar vortex and an unusually long
cold period.

This year's record vortex persisted over the Arctic from
December to the end of March, and the cold temperatures extended
down to a remarkably low altitude, the researchers write.

At altitudes of about 11 to 12 miles (18 to 20 kilometers), more
than 80 percent of the ozone present in January had been
chemically destroyed by late March.

The same dynamics create the infamous ozone hole over Antarctica.
But above the South Pole, ozone is essentially completely removed
from the lower stratosphere ever year. Above the North Pole,
however, ozone loss is highly variable and has, until now, been
much more limited, writes the international research team led by
Gloria Manney of the California Institute of Technology.

Countries agreed to end their production of the substances
ultimately responsible for destruction of the ozone in 1987 with
the Montreal Protocol. However, these pollutants, including
chlorofluorocarbons, still linger in the atmosphere. Ozone
loss is expected to improve in the coming decades as
atmospheric levels of these chemicals decline.

On the Earth's surface, ozone is a pollutant, but in the
stratosphere it forms a protective layer that reflects
ultraviolet radiation back out into space. Ultraviolet rays can
damage DNA and lead to skin cancer and other problems.

Global warming is implicated in the loss of Arctic ozone because
greenhouse gases trap energy lower down, heating up the
atmosphere nearer the ground but cooling the stratosphere,
creating conditions conducive to the formation of the reactive
chemicals that break apart the three-oxygen molecules of ozone.